Effects of Nitrogen Fertilizer on Nitrogen Accumulation, Translocation and Nitrogen Use Efficiency in Rapeseed ( Brassica napus L.)

Abstract

In this study, five conventional oilseed rape varieties with different oil contents, including Yangyou 6(YY6), Suyou 211(SY211), Ningyou 20(NY20), Zhongshuang 11(ZS11), and Zheyou 50(ZY50) were grown under three N(nitrogen) fertilizer levels: 120(N1), 240(N2), and 360 kg N ha-1(N3) from 2010 to 2012. The effects of N application on N accumulation, N translocation rate and N use efficiency were studied through plant sampling, picking deciduous leaf and measuring dry matter weight, N content and oil content. The results showed that with increasing N application rates yield and total N amount in whole plant increased, and N harvest index(NHI) and N use efficiency for grain production(NUEg) decreased. The N translocation rate in leaf ranged from 76.6% to 80.2%, and there were no significant differences among different N fertilizer levels. The nitrogen translocation rate in stem ranged from 36.0% to 57.6%, and decreased with increasing N application rates. The N proportion of deciduous leaf to whole plant ranged from 14.9% to 20.3%, and increased with increasing N application rates. The N proportion of the beginning of flowering stage to ripening stage was from 75.5% to 90.5%, and increased with increasing N application rates. The effect of N amount at the beginning of flowering stage on yield is significant. N application at earlier stage promotes flower bud differentiation and increases effective pods, resulting in higher yield.